All,
The Gmail Security team has updated the trusted root list for Gmail S/MIME as follows
CN=Security Communication RootCA3,O=SECOM Trust Systems CO.\,LTD.,C=JP
SHA256 Thumbprint: 24a55c2ab051442d0617766541239a4ad032d7c55175aa34ffde2fbc4f5c5294
SHA256 Thumbprint: 9a6ec012e1a7da9dbe34194d478ad7c0db1822fb071df12981496ed104384113
SHA256 Thumbprint: be6c4da2bbb9ba59b6f3939768374246c3c005993fa98f020d1dedbed48a81d5
SHA256 Thumbprint: 3a0072d49ffc04e996c59aeb75991d3c340f3615d6fd4dce90ac0b3d88ead4f4
The new trusted root list is now in effect and we will follow up with an update to the CA certificates trusted by Gmail for S/MIME Help Center article.
Thank you
-Erhan, on behalf of the Gmail Security team